1. Field of the Invention
The present invention relates to the field of display techniques, and in particular to a method for obtaining liquid crystal display (LCD) charging ratio.
2. The Related Arts
The liquid crystal display (LCD), or LCD panel, provides the advantages of thinness, power-saving, no radiation, and so on, and is widely applied to, such as, liquid crystal TV, smart phone, digital camera, tablet PC, PC monitor, or notebook PC, and stays as a leading technology in panel display.
The operation principle behind the LCD is to pour liquid crystal (LC) molecules between the thin film transistor (TFT) array substrate and the color filter (CF) substrate, and then apply a driving voltage to the two substrates to control the rotation direction of the LC molecules to refract the light of the backlight module r to produce the image.
Refer to FIG. 1. The active area AA of the LCD has a plurality of pixels P arranged in an array, with each pixel further comprising a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B, arranged in the longitudinal direction. Each sub-pixel is electrically connected to a TFT T, the gate of the TFT T is connected to the scan line 100 extending in the lateral direction, the source is connected to the data line 200 extending in the longitudinal direction, and the drain is connected to the pixel electrode PX. Typically, a pixel P corresponds to a data line 200 and three scan lines 100, which is referred to as tri-gate architecture. Applying the gate scan signal Gate to the scan line 100 will cause all the TFTs T connected to the scan line 100 to turn on. Then, applying the data signal Data to the data line 200 will be able to write into corresponding sub-pixel to control the LC transmittance to achieve color and brightness control.
The charging ratio is an important index for LCD as the value directly affects the brightness, transmittance, display quality of the LCD. Refer to FIG. 2. The charging ratio is computed as:CRatio=(Vpixel/Vdata)×100%
Wherein Vdata is the voltage of the data signal Data when the gate scan signal Gate is in effect, and Vpixel is the peak value of corresponding pixel voltage after charging sub-pixel.
In general, as shown in FIG. 2, the duration when the gate scan signal Gate is in effect is equal to the duration when the data signal Data is in effect. Without pre-charging, the LCD charging ration is relatively low. To increase charging ratio, as shown in FIG. 3, the duration when the gate scan signal Gate is in effect can be set longer than the duration when the data signal Data is in effect. As such, in pre-charging, the LCD charging ratio is increased.
The conventional process to obtain the LCD charging ratio comprises:
identifying pixel layout;
identifying the thickness and electric parameters, such as, conductivity, dielectric constant, and so on, of each film layer forming the pixel;
extracting related electric parameters of resistors, capacitors;
establishing a model card of the TFT based on the TFT characteristics inside the sub-pixel;
establishing a SPICE model based on the LCD driving method;
obtaining pixel voltage by analogy, and computing charging ratio.
The aforementioned conventional method has obvious shortcoming: the charging ratio only has simulation result, the accuracy cannot be ensured, and cannot be verified through experiment.